Organometallic compounds



United States Patent 3,214,452 ORGANOMETALLEC COMPOUNDS Robert P. M.Werner, Binningen, Basel-Land, Switzerland, and Harold E. Podall,Arlington, Va., assignors to Ethyl Corporation, New York, N.Y., acorporation of Virginia No Drawing. Filed Apr. 23, 1962, Ser. No.139,292

12 Claims. (CL 260429) This application is a continuation-in-part ofapplications Serial Nos. 80,542 and 80,543, both filed January 4, 1961,and both now abandoned.

This invention relates to a process for forming novel organometalliccompounds. More specifically, the invention relates to a process forforming alkali and alkaline earth metal-etherate salts of Group VBmetals in which the metal is present in the form of an anion containingthe metal atom having six carbonyl groups bonded to it.

An object of this invention is to provide a novel process for preparingorganometallic compounds of Group VB metals. A further object is toprovide a process for producing stable alkali metal and alkaline earthmetal-etherate salts of vanadium, tantalum, and niobium hexcarbonylanions. Additional objects will become apparent from the followingdiscussion and claims.

The objects of our invention are accomplished by providing a process inwhich a reducing metal, which is an alkali metal or an alkaline earthmetal, is reacted with a Group VB metal (vanadium, niobium, or tantalum)salt in the presence of an ether solvent and carbon monoxide pressure.The alkali and alkaline earth metal-etherate salts of a Group VBmetal-hexacarbonyl anion are prepared by this process. The saltsproduced from our process are most unusual in that they contain an anionhaving a charge of minus one in which the negative charge is centeredsolely on the Grooup VB metal atom. This makes the anion a potentreductant so that it can be readily employed in forming other compoundsvia an oxidation-reduction type of mechanism.

As set forth above, our process involves reaction between .a reducingmetal and a Group VB metal salt in the presence of an ether solvent andunder carbon monoxide pressure. The alkali metals which may be employedas reductants are lithium, sodium, potassium, rubidium and cesium. Thealkaline earth metals which may be employed are calcium, strontium,barium, and magnesium. In addition, zinc or aluminum may be employed asthe reducing metal. Preferably, the reducing metal is an alkali metaland most preferably it is sodium. Also, mixture of the above reducingmetals may be employed in our process. As an example, we can employ amixture of sodium and potassium as the reductant in our process.

The reducing metal employed in our process should be in a highly activeform. In the case of the alkali metals this is conveniently accomplishedby employing the metal in the fluidized suspension in an inert liquid.Examples of such suspensions are finely divided sodium or potassium inmineral oil or par-afiin. Also, certain of our reducing metals can beplaced in a reactive form by amalgamating them. One example of this is amagnesium amalgam. Other forms of activating the reducing metal involveusing, for example, freshly prepared metal turnings which employ a largesurface area of the freshly cut metal.

The alkali or alkaline earth metal which is employed as a reductant isgenerally employed in at least a 50 percent excess over thattheoretically required to reduce the metal in the Group VB metal salt toa valence state of minus one. Thus, if the Group VB metal salt employedis vanadium trichloride, 4 moles of sodium would be required to reduceone mole of the vanadium reactant. In order to insure that the desiredreduction takes place,

3,214,452 Patented Oct. 2%, 1965 Ice however, 6 moles of sodium wouldgenerally be employed in the process.

The Group VB metal salt which is employed as a reactant in the processis preferably a metal halide or oxyhalide although other similar saltsmay be employed if desired. The ether solvent may be a cyclic orstraightchain ether and can contain one or a plurality of oxygen etherlinkages. Preferably, the ether solvent is a tridentate ether which isto say that it contain-s 3 ether oxygen linkages in the molecule. Thetridentate ethers are preferred because the tridentate ether-saltsformed from our process are more stable than salts which contain amonodentate or a bidentate ether. As evidence of the great stability ofthe tridentate ether salts, we have found that sodiumbis(diethyleneglycol dimethylether) hexacarbonyl van-adate can berecrystallized from diethylether without solvent exchange between thediethylether and the diethyleneglycol dimethylether.

The ether is generally employed in a large excess since the ethergenerally functions as both a reactant and solvent. The preferred ethershave low toxicity and are compatible with a wide range of reducingmetals. They can be employed in large quantity without the use ofelaborate safety precautions. Typical ethers which are representative ofthose we employ in our process are dibutylether, dioxane,diethyleneglycol dibutylether, ethyleneglycol diethylether, anddiethyleneglycol dimethylether. Other ethers such as diethylether can beemployed.

As stated previously, our process is carried out under carbon monoxidepressure. Since the time required for reaction is dependent to somedegree upon the carbon monoxide pressure, we can conduct the processover a relatively wide range of carbon monoxide pressures using acorrespondingly wide range of reaction times. Generally, carbon monoxidepressures ranging from 1,000 to 10,000 p.s.i. may be employed.Preferably, however, the carbon monoxide pressure employed rangesbetween about 3,000 to about 8,000 p.s.i. since Within this range yieldsare maximized while reaction time is minimized.

Our process may be carried out over a temperature range from about 60 C.to about 150 C. Higher temperatures than about 150 C. tend to increasethe amount of decomposition occurring in the reaction and temperatureslower than about 60 C. tend to increase the reaction time beyond apractical limit. Preferably, our process is carried out at a temperatureof about C. since at this temperature, yields are maximized whileundesired side reactions are minimized. Generally, our process iscarried out with agitation of the reaction mixture since it is foundthat this insures a more even reaction rate.

As stated previously, the time required for our process is not a trueindependent variable, but is dependent to some degree upon the otherprocess conditions employed. Thus, for example, if a relatively hightemperature, a relatively high carbon monoxide pressure, a high degreeof agitation are employed, the reaction time will be reduced. If on theother hand, a relatively low temperature, a relatively low carbonmonoxide pressure, and slight agitation are used, the reaction time willbe proportionately increased. In practice, the necessary reaction timeis easily determined since one can trace the course of the reaction byobserving the variation in carbon monoxide pressure in the reactionsystem. As the reaction proceeds, carbon monoxide is used in thereaction and a substantial pressure drop occurs. When the pressureceases to drop, this is evidence that the reaction is completed and thereaction product can be discharged. In general, from about one to about40 hours reaction time is sufficient although, as stated above, otherreaction times can be employed if the process conditions are variedaccordingly.

Since our process is carried out under carbon monoxide pressure, thereis generally no need to employ a protective gas such as nitrogen,helium, argon, krypton or the like in the reaction system. Such gasesmay be employed, however, if it is desired to increase the pressurewithout increasing the quantity of carbon monoxide in the reactionvessel.

In conducting our process, the order of mixing the reactants isfrequently of some importance. Experiments have demonstrated that someof the Group VB metal salts which are employed as reactants, especiallythe niobium and tantalum salts, react with the ether solvent to form aproduct which does not react as readily to form the desired alkali metalor alkaline earth metal-etherate Group VB metal hexacarbonyl salt.

Three experiments were carried out to determine the behavior of tantalumpentachloride with ethers. The first experiment (a) consisted of adding6.0 parts of TaCl to 90 parts of diethyleneglycol dimethylether (DMC).Experiment (b) consisted of adding 6.0 parts of TaCl to 90 parts ofdimethoxyethane (DME). In experiment (c), a like amount of TaCl wasadded to 90 parts of tetrahydrofuran (THF). All three experiments werecarried out under nitrogen. Temperature increments of 5, 6, and 7 C.were noted respectively. The colors of mixtures (a) and (b) wereblue-black, while mixture (c) was chalky brown. The mixtures werestirred for two hours and filtered. A grey residue was obtained from(a), while (b) yielded a greater amount of black residue. No residue wasobtained when mixture (c) was filtered. The filtrate from (c) wasevaporated to dryness and the dry solids were hydrolyzed with H O. Thehydrolyzed solids and residues from (a) and (b) were analyzed. Residue(a) contained 38.9 percent tantalum and 30.7 percent chlorine. Residue(b) contained 41.8 percent tantalum and 31.7 percent chlorine. Thehydrolyzed solids from (0) contained 17.9 percent tantalum and 10percent chlorine. Assuming the difference in each case was due tosolvent, the results indicate the formation of alkoxides. The alkoxidesdecrease the availability of the metal. The alkoxide products were:

Residue (a)=TaCl (DMC) Residue (b)=TaCl (DME) Residue (c) =TaCl (THF)These alkoxides are undesired and can be substantially eliminated bycarefully observing certain procedures in the mixing of the reactants.In order to diminish this undesirable side reaction, we have found thatthe Group VB metal reactant should be added directly to the pressurizedreaction vessel containing the reducing metal and the ether, both asdescribed previously, and the carbon monoxide under pressure. The GroupVB metal reactant is added rapidly and reacts quickly with both thereducing metal and ether to form the desired product before theundesired side reaction can take place. On a relatively small scale, oneconvenient way of adding the Group VB metal reactant to the reactionvessel is to place it in a sealed vial made of a frangible material. Thevial is placed in the reaction vessel along with the other reactants andthe vessel is sealed and pressurized with carbon monoxide. The agitationmechanism is then started and the vial is broken when the agitatorstrikes it so as to quickly release the Group VB metal reactant into thesystem.

Of the Group VB metal salts we employ in our process, those of vanadiumdo not tend to react rapidly with the ether solvent. Thus, in the caseof vanadium it is not necessary to follow the above procedure in mixingthe reactants. In the case of tantalum and niobium reactants, however,it is necessary to follow the above mixing procedure since thesecompounds have a greater tendency to react directly with the ethersolvent.

Of the Group VB metal reactants, certain are preferred for use in ourprocess. The halides, and particularly the chlorides, are preferredreactants since they are relatively cheap and readily available.Examples are the vanadium trihalides, such as vanadium trichloride,tantalum pentachloride, and niobium pentachloride.

The products formed from our process are readily separated from theliquid reaction mixture. The reaction product is generally firstfiltered to remove any' insoluble residue including any excess reducingmetal. After this operation the products are readily precipitated fromthe filtrate by adding to it a hydrocarbon such as petroleum ether,nonane, hexane, or the like. After the product has precipitated, it canthen be separated by means of filtration, decantation of the liquid,centrifugation and the like.

To further illustrate our process, as defined above, there are presentedthe following examples in which all parts and percentages are by weightunless otherwise indicated.

Example I A mixture comprising 47.2 parts of vanadium trichloride, 41.5parts of sodium as a 50 percent dispersion in mineral oil and 810 partsof diethyleneglycol dimethylether, which had been distilled oversodiobenzophenone, was charged to a reaction vessel. The reaction vesselwas then pressurized to 3,000 p.s.i. with carbon monoxide and heatedwhile agitating the reaction mixture. The reaction mixture was so heatedat 100 C. for 20 hours during which time the reaction temperature wasraised briefly to 150 C. The reaction vessel was then cooled and ventedto relieve the carbon monoxide pressure and the reaction product wasdischarged. After filtration of the reaction product under a nitrogenatmosphere, petroleum ether was added to the stirred clear yellowfiltrate. The resulting oil was triturated with fresh petroleum ether toyield parts of crude yellow solid. This material was soluble in ether,water and acetone and insoluble in petroleum ether. The material wasthen recrystallized from ether to produce a bright yellow crystallinesolid having a melting point of 176 C. with decomposition. The productwas relatively stable in air. An aqueous solution of the yellowcrystal-material showed an alkaline pH and was strongly reducing. As anexample of its reductive properties, the compound was capable ofreducing sulfuric acid to hydrogen sulfide in diethyleneglycoldimethylether. On analysis, there was found: C, 42.5; H, 5.52; V, 10.1;Na, 4.68. Calculated for C H NaO V: C, 42.37; H, 5.53; V, 9.98; Na, 4.50percent. Further, the compound was subjected to magnetic susceptibilitymeasurements and was found to be diamagnetic. The properties, analysis,and infrared absorption spectrum of the compound showed it to be sodiumbis(diethyleneglycol dimethylether) hexacarbonyl vanadate, having theempirical formula A sealed glass tube containing 79 parts of tantalumpentachloride was placed in a reaction vessel so that the tube would bebroken when the agitator was started. The reaction vessel was chargedwith 57 parts of sodium (50 percent dispersion) in 720 parts ofdiethyleneglycol dimethylether. The reaction vessel was closed andpressured to 4,000 p.s.i. with carbon monoxide. A sample of gas from thevessel amounting to 1,000 p.s.i. was vented and analyzed for oxygen. Theoxygen content was less than 0.01 percent. The vessel was repressured to4,000 p.s.i. and heated to C. over night. The total heating time was 23hours. After that time, the vessel was discharged and rinsed withdiethylether. The products were filtered under nitrogen and trituratedwith petroleum ether. A small yield of sodium bis (diethylene- Example111 In the same manner as in Example II, 39.0 parts of niobiumpentachloride were reacted with 40 parts of sodium in the presence ofdiethyleneglycol dimethylether solvent. The niobium pentachloride wasadded to the reaction vessel in a glass tube which was broken after thevessel had been pressurized with carbon monoxide. After heating at 100C. under a carbon monoxide pressure of 4,000 p.s.i. for about 20 hours,the reaction vessel was discharged. The product was separated from thereaction mixture in the manner employed in Example II. A small yield ofsodium bistdiethyleneglycol dimethylether) hexacarbonyl niobate wasobtained.

Example IV Vanadium tetrachloride, 193 parts, is charged to a reactionvessel and mixed with 2800 parts of diethyleneglycol dimethylether whilecooling the mixture. There is then added to the reaction Vessel 160parts of sodium in the form of a suspension in mineral oil. T hereaction vessel is pressurized to 5,000 p.s.i. with carbon monoxidewhile cooling the reaction mixture. The reaction mixture is thenagitated at 120 C. for 24 hours after which the reaction vessel iscooled and excess carbon monoxide pressure is released 'by venting. Thereaction product is discharged, filtered and petroleum ether is added tothe filtrate to give in good yield a precipitate of sodiumbisfidiethyleneglycol dimethylether) hexacarbonyl vanadate.

Example V Vanadium oxytrichloride, 210 parts, is mixed withdiethyleneglycol dibutylether and charged to a reaction vessel. Twohundred eighty-tour parts of 50-50 sodiumpotassium all-0y suspended :indiethyleneglycol dibutylether is then added to the reaction vessel. Thetotal quantity of diethyleneglycol dibutylether in the reaction vesselis 2010 parts. The reaction vessel is then heated to 110 C. at a carbonmonoxide pressure of 4,000 p.s.i. and held at this temperature for 36hours. The reaction vessel is then cooled; excess carbon monoxidepressure is released by venting, and the reaction product is discharged.On filtration, followed by addition of petroleum ether to the filtrate,an oily recipitate of a mixed sodiumpotassium hexacarbonylvanadate-diethyleneglycol d-ibuty-lether salt is obtained. This reactionillustrates that ethers having up to about 12 carbon atoms are operablein the process.

Example VI A suspension comprising 200 parts of potassium adrnixed with2250 parts of dimethoxyethane is charged to a reaction vessel. There isthen added 290 parts of vanadium tribromide in a |frangible vial. Oncharging the reaction vessel with carbon monoxide to a pressure of 5,000p.s.i., the agitation mechanism is started so as to break the frangiblevial and release the vanadium tribromide. The reaction mixture is thenheated to 60 C. for hours after which the reaction vessel is cooled,vented, and the reaction product is discharged. On filtration, followedby addition of petroleum ether to the filtrate, a good yield ofpotassium tris(dirnethoxyethane) hexacarbonyl vanadate is obtained.

Example VII Tantalum pentabromide, 580 parts (enclosed in a frangiblevial), 120 parts of amalgamated magnesium and 1800 parts of dioxane arecharged to a reaction vessel which is then pressurized to 5,000 p.s.i.with carbon monoxide. The reaction vessel is then heated to 100 C. atwhich time the agitator is started and the frangible vial is broken soas to release the tantalum penta'bromide react-ant. After heating for 40hours at 100 C. the reaction vessel is cooled and vented. The reactionproduct is 6 filtered, petroleum other is added to the filtrate andthere is obtained a sticky solid containing a hexacarbonyl tantalatesalt.

Example VIII To a reaction vessel containing 210 parts of a mineral oilsuspension of sodium and 1800 parts of dimethoxyethane is added 35 8parts of tantalum pentachloride which is enclosed in a frangible vial.The reaction vessel is then pressurized to 4,000 p.s.i. with carbonmonoxide and the vial is broken by starting the agitator. After heatingat C. for 36 hours, the reaction vessel is discharged. The product,sodium bis(dimethoxyethane) hexacarbonyl tantala-te, is separated fromthe reaction product by the procedure used in Example I.

Example IX To a reaction vessel is added 493 parts of niobiumpent-abromide enclosed in a frangible vial and 360 parts of a potassiumsuspension in 2800 part-s of diethyleneglycol dimethylether. Thereaction vessel is pressurized to 6,000 p.s.i. with carbon monoxide,heated to C. and agitated. On agitation, the frangible vial is brokenand the niobium pentabromide is released into the system. After heatingfor 30 hours at 110 C. the reaction vessel is cooled and excess carbonmonoxide pressure is released by venting. The reaction product is thendischarged, filtercd, and petroleum ether is added to the filtrate toproduce a precipitate of potassium tris(diethyleneglycol dimethylether)hexacarbonyl niobate.

The compounds produced by our process are quite useful in :metal platingapplications. In order to use our compounds in metal plating, they arefirst converted to a tetraalkylammonium hexacarbonyl Group VB metalsalt. This is conveniently accomplished by reacting a tetraalkylammoniumcompound such as tetramethylammonium bromide with the alkali or alkalineearth metal-etherate salt of the hexacarbonyl Group VB metal anion. Asshown previously in Example II, there is obtained from this reaction thetetraalkylammonium hexacarbonyl Group VB metal salt (in that casetetramethylammonium hexacarbonyl tantalate). These salts can bedecomposed so as to deposit a metal-containing coating on a surfacewhich it is desired to plate. Since the tetraalkyla-mmonium salts arenot volatile, the plating is accomplished by bringing :a heated object,whose temperature is above the decomposition temperature of thetetraalkylammonium salt, into contact With the salt. This results indecomposition of the salt and the formation of a Grou VBmetal-containing coating on the heated object.

Another method by which plating can be accomplished is to coat thesurface of the object to be plated with the tetraalkylammonium salt ofthe Group VB metal hexacarbonyl anion and then to heat the coated objectto a temperature above the decomposition temperature of thetetraalkylarnmonium salt. This also results in forming ametal-containing coating on the object to be plated.

To further illustrate our method for forming coatings containing a GroupVB metal, there is presented the following example.

Example X A glass cloth band weighing one gram is dried for one hour inan oven at C. It is then cover-ed with a thin layer oftetramethylammonium hexacarbonyl tantalate and is placed in a containerwhich is devoid of air. The container is heated to a temperature of 500C. for one hour after which time it is cooled and opened. The cloth iscoated with a tantalum-containing coating, has a metallic greyappearance, and exhibits a slight gain in weight.

As shown by the previous example, the compounds formed from our processcan be converted to their tetraalkylammonium salts which can be utilizedin forming metal-containing coatings. These coatings are not onlydecorative but serve also to protect the underlying substrate materialfrom corrosion.

Having fully defined the novel compounds of our invention, their mode ofpreparation and their utility, we desire to be limited only within thelawful scope or the appended claims.

We claim:

1. A process for the preparation of alkali and alkaline earthmetal-etherate salts of a Group VB metal hexacarbonyl anion, saidprocess comprising reacting a reducing metal selected from the classconsisting of alkali and alkaline earth metals, with a Group VB metalsalt selected from the class consisting of inorganic Group VB metalhalides and inorganic Grou VB metal oxyhalides with a saturated,unsubstituted ether selected from the class consisting of monodentate,bi-dentate and tridenta-te ethers having up to about 12 carbon atoms,and carbon monoxide under a pressure between about 3000 to about 8000psi. and subsequently separating said metal-etherate salt from theresultant reaction mixture by treating said reaction mixture withpetroleum ether to remove said metalether-ate salt from solution.

2. The process of claim 1 in which the reducing metal is an alkalimetal.

3. The process of claim 2 in which the ether is a saturated,unsubstituted tridentate ether having up to about 12 carbon atoms.

4. The process of claim 3 in which the alkali metal is sodium.

5. The process of claim 4 wherein the tridentate ether isdiethyleneglycol dimethylether.

6. The process of claim 5 in which the process is carried out betweenabout 60 C. to about 150 C.

7. The process of claim 6 in which the reaction temperature is about 100C.

wherein Et. is diethyleneglycol dimethylether and M is a Group VB metal.

12. Organometallic compounds having the formula wherein Et. is anon-cyclic, saturated, unsubstituted tridentate ether molecule having upto 12 carbon atoms, and M is an atom of a Group VB metal.

References Cited by the Examiner UNITED STATES PATENTS 2,870,180 l/59K-ozikowski et al. 260-429 2,882,288 4/59 Brantley et al 2604293,060,212 10/62 Brown et al 260-429 FOREIGN PATENTS 1,147,868 6/57France.

OTHER REFERENCES Vigoureux, Uber gemischte Mono-cyclopentadienylmetallkomplexe des Vanadins, May 26, 1959.

J.A.C.S., vol. 82, June 5, 1960, pp. 2966 and 2967.

TOBIAS E. LEVOW, Primary Examiner.

12. ORGANOMETALLIC COMPOUNDS HAVING THE FORMULA